Allergens constitute the most abundant proteins of grass pollen, which is the major cause of allergic disease in temperate climates (Marsh (1975) Allergens and the genetics of allergy; in M. Sela (ed), The Antigens, Vol. 3, pp 271-359, Academic Press Inc., London, New York)., Hill et al. (1979) Medical Journal of Australia 1, 426-429). The first descriptions of the allergenic proteins in ryegrass showed that they are immunochemically distinct, and are known as groups I, II, III and IV (Johnson and March (1965) Nature, 206, 935-; and Johnson and Marsh (1966) Immunochemistry 3, 91-100). Using the International Union of Immunological Societies' (IUIS) nomenclature, these allergens are designated Lol pI, Lol pII, Lol pIII and Lol pIV.
These four proteins have been identified in pollen ryegrass, Lolium perenne L., which act as antigens in triggering immediate (Type 1) hypersensitivity in susceptible humans.
Lol pI is defined as an allergen because of its ability to bind to specific IgE in sera of ryegrass-sensitive patients, to act as an antigen in IgG responses and to trigger T-cell responses. The allergenic properties have been assessed by direct skin testing of grass pollen-sensitive patients. The results showed that 84% had a skin sensitivity to Lol pI (Freidhoff et al., (1986) J. Allergy Clin. Immunol. 78:1190-1201) demonstrating the primary importance of this protein as the major allergen. Furthermore, 95% of patients demonstrated to be grass pollen-sensitive possessed specific IgE antibody that bound to Lol pI, as demonstrated by immunoblotting (Ford and Baldo (1986) International Archives of Allergy and Applied Immunology 81:193-203).
Substantial allergenic cross-reactivity between grass pollens has been demonstrated using an IgE-binding assay, the radioallergo-sorbent test (RAST), for example, as described by Marsh et al. (1970) J. Allergy, 46, 107-121, and Lowenstein (1978) Prog. Allergy, 25, 1-62. (Karger, Basel).
The immunochemical relationship of Lol pI with other grass pollen antigens have been demonstrated using both polyclonal and monoclonal antibodies (e.g. Smart and Knox (1979) International Archives of Allergy and Applied Immunology 62:173-187; Singh and Knox (1985) International Archives of Allergy and Applied Immunology 78, 300-304). Antibodies have been prepared to both purified proteins and IgE-binding components. These data demonstrate that the major allergen present in pollen of closely related grasses is immunochemically similar to Lol pI (Singh and Knox, supra).